Dilation Optimisation for Uniform Bioprosthetic Leaflet Expansion

The goal of this clinical trial is to discover if routine 'double tap' balloon post-dilation improves valve expansion and clinical outcomes in adults undergoing Transcatheter Aortic Valve Implantation (TAVI) with the SAPIEN balloon-expandable TAVI prosthesis. The primary hypothesis is that routine 'double tap' balloon post-dilation improves TAVI valve expansion. The secondary hypothesis is that routine 'double tap' balloon post-dilation improves TAVI valve haemodynamic performance. Participants will be randomised to balloon-expandable TAVI either with or without routine 'double tap' balloon post-dilation.

The ACE-DOUBLE trial will be a multicentre, registry nested, block randomized, open label clinical trial comparing routine versus discretionary balloon post-dilation strategies following TAVI using the SAPIEN 3 balloon-expandable THV for severe aortic stenosis (AS). Patients with severe symptomatic aortic valve disease that are accepted for TAVI using a balloon-expandable THV. Currently, the only balloon-expandable THV in routine clinical practice in Australia are the Sapien 3 Ultra and Sapien 3 Ultra Resilia (Edwards Lifesciences, Irvine CA, USA). Patients will be recruited from three TAVI centres participating in the ACE registry: The Alfred Hospital, Cabrini Hospital and Epworth Hospital are all located in Melbourne, Australia. Specific sub-groups may benefit more from balloon post-dilation (BPD), and hence exploratory analyses will be performed to examine the effect of BPD on primary endpoints in the following subgroups: * Male vs Female * Pre-dilation vs no pre-dilation * Tricuspid vs bicuspid aortic valve * Very severe AS (mean pressure gradient \> 50mmHg) * Very aortic valve high calcium score (\>3000 in males, \>1900 in females)

Inclusion Criteria: * Severe aortic stenosis undergoing trans-femoral TAVI using the SAPIEN 3 Ultra/RESILIA balloon-expandable transcatheter heart valve. * Tricuspid or bicuspid aortic valve stenosis Exclusion Criteria: * Valve-in-valve TAVI for failure of an existing prosthetic surgical or transcatheter valve failure * TAVI performed for native valve aortic regurgitation * High risk 'hostile' annular anatomy as adjudicated by multidisciplinary Heart Team based on pre-procedure CT anatomy.